Post-release monitoring

Monitoring methods

Indirect effects on other trophic levels and food webs

Specific recommendations in this area are extremely difficult, and studies
need to be designed on a case-by-case basis. In general, the ecology of the
system within which non-target parasitism is occurring needs to be very well
known if realistic indirect effects are to be measured. The ultimate goal of the
release of biological control agents is the restoration of invaded ecosystems.
Uninvaded reference sites or long-term documentation of communities before
release of biological control agents would provide useful benchmarks
(Blossey 1999). The current poor availability of biological inventories will make true
assessments of indirect impacts on food webs and species difficult. Monitoring
protocols need to be able to detect the extent to which the release of
biological control agents can drive population fluctuations or changes in
ecosystem function. Natural ecosystems are immensely complex, although invaded
systems may have lost a degree of their original complexity. However, the
prevalence of organism interactions makes it difficult to predict the response
of even well-understood systems to environmental change or perturbations
(Yodzis 1988, Polis and Strong 1996). Consequently, arguing with confidence that
conditions have ecologically improved or deteriorated, or are simply different
due to changes associated with spread of biological control agents, is
impossible unless such impacts can reliably be distinguished from natural
oscillations or plant succession. Lag effects make the detection and mitigation
of impacts even more challenging (Byers and Kendall 1982, Parker et al. 1999).
Laboratory and small-scale field experiments can not adequately replicate
interactions that occur in the field. The only way to capture the full range of
ecological effects of the release of biological control agents is by detailed
observations in actual ecosystems.